Field of the Invention
The present invention relates to curable epoxy resin compositions; and more specifically; to ultraviolet light (UV) curable divinylarene dioxide resin compositions; and UV cured products prepared from such curable divinylarene dioxide resin compositions. The curable divinylarene dioxide resin compositions of the present invention are advantageously useful in, for example, UV curable ink formulations.
Description of Background and Related Art
Radiation- or thermally-initiated, cationically-curable epoxide monomers and compositions are disclosed in U.S. Pat. No. 5,962,547 (herein “the '547 patent”). In particular, cationically-curable epoxides described in the '547 patent are compounds containing a styrene oxide monomer. The '547 patent also describes that the cationically-curable epoxide compounds are useful in adhesive and coating formulations. For example, a UV-curable epoxide adhesive formulation includes (i) a cationic photoinitiator; (ii) an alcohol or polyol; and (iii) the styrene oxide monomer as the epoxide component.
A problem encountered with certain styrene oxide monomers described in the '547 patent is poor stability with respect to hydrolysis. Significant amounts of water are frequently incorporated into curable UV ink formulations unintentionally by exposure to the atmosphere and as a contaminant in formulation components. Subsequent hydrolysis of the epoxy monomer in the formulation produces glycol groups and has adverse affects on formulation processability and cured ink properties.
Also, prior art processes for curing UV ink formulation suffer from several disadvantages including low speed UV processing, high viscosity, and odor associated with UV processing. In other words, the prior art processes do not disclose the combination of high speed UV processing, low odor, and good adhesion to substrates.
Accordingly, there is still a need in the industry to provide a photocationically-curable epoxy resin having good hydrolytic stability with (1) high speed UV processing and (2) low odor UV processing.